Colloids are particles or droplets which are finely distributed in the dispersion medium (solid, gas or liquid). The sizes of the individual particles are typically in the nanometer or micrometer range. If they are mobile – e.g. in a liquid dispersion medium – they usually show Brownian motion. Colloidal suspensions are of great importance in the food and cosmetics industry as well as in basic research, in particular in statistical physics. Colloid chemistry is the field of chemistry that deals with its material properties.